Telephone system



July 25, 1933- J. A. BURGENER TELEPHONE SYSTEM Filed Dec. 29. 1931Patented July 25, 1933 UNlTED STATES.

PATENT oFFlcE..

Jomr A. BUBGENB., or nINsDALn. ILLINOIS, AssIe'Non, BY MESNE-ASSIGNMENTS; To

.ASSOCIATED-ELECTRIC LABORATORIES, INC., OF CHICAGO,

TION 0F DELAWARE TELEPHONE SYSTEM Application led December 29', 1981.Serial No. 583,667.

The present invention relates to telephone systems in general, but ismore particularly concerned with telephone systems wherein thesubscribers lines are classified and where in provisions are made forinforming the telephone operator answering a call of the class to whichthe calling line belongs; and the main object, broadly stated, is toprovide a more refined and satisfactory arrangement for notifying theoperator of the class in.

which the calling line belongs.l

General description connection to a manual switchboard by Way of a trunkline leading from the automatic switchboard to the manual switchboard,the manual operator is signalled; while, at the same time, the releasetrunk conductor ofthe connection established from the calling line tothe automatic-to-manual trunk line is in ductively coupled with thetalking circuit, so that, when the operator answers, any tone currentplaced on the release-trunk conductor of the established connection byway of the subscribers individual line equipment is heard by theoperator fora predetermined interval of time after the operatorresponds. Now, it often happens during certain s ocalled busy periodsthat the manual operator is unable to respond promptly, with the resultthat several unanswered connections may extend to her switchboard at thesame time. With the tone current being simultaneously applied to severalof the interswitchboard trunk lines, which are often eX- teuded from oneofiice to another, and therefore of considerable length, some diiicultyis experienced in preventing the tone current from being induced in theparallel trunk lines Y which conversation is being carried out maybecome of annoying magnitude when tone current is'being continuouslyapplied to several trunk lines over which unanswered connections havebeen extended to the manual switchboard. If the ap lication oftone'current to an inter-switch oard trunk line is made lonly after theoperator responds and then only for a long enough time to enable theoperator to distmguish the character of application of the distinctivetone current to the inter-switchboard trunk line responsive to the-callbeing answered by the operator and for automatically discontinuing theapplication of tone current at the end of a predetermined interval longenough to enable the operator to distinguish the character of the tonesignal;

It is understood, of course, that systems have been developed heretoforewherein the applica tion ofA tone current to the interswitchboard trunkline is made only after the operator responds and is terminated afterthe operator has heard and distinguished the characteristic tone signal;but, as ar as applicant is aware, this is the first time that thisoperation has been performed entirely automatically responsive to thesimple answering act of the operator performed in the usual manner andwithout necessitatin a special key manipulation or other simi ar specialacts on the part of the operator to initiate or terminate theapplication of the tone current.

Description of drawing Referring now to the accompanying single sheet ofdrawing, the showing therein is similar to the showing in the drawingsin the Tharp application hereinbefore referred to; the main differencelies in the arrangement employed in the .so-called repeater or trunkcircuit TC connected on the automaticswitchboard end of theinter-switchboard trunk line comprising conductors 23 and 24.

minates at the manual switchboard in a jack;

such as the jack J, illustrated, and each trunk line has a line circuitassociated therewith at the switchboard, suchas the line circuit LC. Anumber of cord circuits, such as the cord circuit CC, are provided,which cord circuits are preferably o f the general type disclosed inPatent No. 1,802,449, granted April 28, 1931 to A. W. Steinke.

It will be noted that two tone sources are shown associated with thelineswitch LS, the

tone transformers 25 and 26. The operating Acurrent for the operatingmagnet 1 of the lineswitch LS may be obtained through the secondarywinding of either tone transformer dependingupon the class-in which theline of substation A belongs'. As shown, the operating current for thelineswitch magnet is obtained'through the secondary winding of thetransformer 25, through which the first of the two characteristic tonesis supplied, denoting that the line of sub-v station A belongs in thefirst class. -It Will be understood, of course, that the number ofclasses may be extended as desired by providing additional tone sources.

Detailed description The invention having been described generally, adetailed description of the operation of the apparatus shown will now begiven.' For this purpose it will be assumed that the subscriber atsubstation A removes his receiver and dials the digit assigned to themanual switchboard for the purpose of soliciting the aid of the manualoperator in establishing a connection which may not be establisheddirectly through the automatic switchboard.

Seizing the truck circuit T0 When the receiver is removed at substationA, the line relay 3 of the lineswitch LS operates in theusual manner andconnects up the magnet 1 for operation, at the same time enablingswitching relay 2 to operate (as soon as an idle trunk is found) andextend a connection by way of wipers 4 to 6 to thistrunk. Assuming thatthe vtrunk line extending to the selector S is the first one found to beidle, the selector S is seized and thereupon prepared for operation inthe usual manner.

, When the digit assigned to thefswitch-v backbridge relay 11', operatesover the calling line and closes a circuit for release relay 12 at itsupper armature, at the same time reversing the connections between thewindings of back-bridge relay 11 and the talking conductors. .Whenrelease relay 12 responds to the closure of its circuit, it places aground potential on the incoming release trunk conductor 8 by Way of theupper winding of the 'induction coil 14, thereby providin a holdingcircuit for the switches LS and Signalling the operator Release relay l2also places a ground poten-A tial on conductor 4 1, thereby closing acircuit through contacts of relay 17 for the ringing-start relay 15.Relay 15 thereupon operates and locks itself -to conductor'41 by Way ofthe middle-upper armature of relay 11, at the same time, applyingringing current to the trunk conductors 23 and 24 at its upper and lowerarmatures, by way of the corresponding armatures of relay 17. At thesame time, the placing of ground potential on conductor 41 results inthe closure of a circuit through contacts of relay 17 for the timerrelay 16. Relay 16 thereupon operates and closes acircuit for relay 17by Way of contacts of the latter relay. Relay 17 does not respondimmediately to the closure of this circuit, because relay 16 is avibrating-con tact relay, having a weight attached to the contactthereof which causes the contact to vibrate for an interval before acontinuous connection is made.

Stop-ping the flow of ringing current As soon as the contact of relay 16has ceased to vibrate, relay 17 operates and locks itself to conductor41; disconnects relay 16 from conductor 41 and prepares a new circuitfor it,

whel upon relay 16 deenergizes; disconnects the ringing current andcloses points in the talking circuit at its upper and lowerarmatransfers the vibrating contact of relay 16 from its own winding tothe winding of thev ico tures; and at its inner-lower armature it .Theringin flow of current has now been discontinued y the operation ofrelay 17, but relay 15 remains operated in spite of the lopening of itsinitial circuit at contact of relay 17, because of theabove-mentioned-locking circuit established for this relay through itsown inner-upper contacts by Way of middle-upper armature of4 back-bridgerelay 1 1 and conductor41, grounded at contacts of relay 12. l

With relay 15 operated, a characteristic ring-back tone is placed on thelower talking conductor from the ring-backtone conductor 27, indicatingto the calling subscriber that the operator 1s now being signalled.

In the manual office, the above-described momentary application ofringi-ng current to the trunk line causes an operation of the line relay18, whose upper Winding is'normally included in a bridge circuit acrossthe talking conductors of the trunk line. Upon o erating, relay 18closes a locking circuit or its lower winding at its lower contacts, andat its upper contacts it closes a circuit for the lamp L to signal theoperator.

T he operator answers The operator responds Vto the lighting of the lampL by insertin the plug of an idle cord circuit, the plug of the cordcircuit CC for example, into the jack J. When this energizes over thetalking conductors of the trunk line in series with back-bridge relay 11of the trunk circuit TC. With relays 2O and 21 operated, a circuit isclosed through contacts of both relays for the connecting relay 22,which operates to connect the operators headset conductors 29 and 30across the talking strands of the cord circuit.

Apply/ng the class-tone current In the trunk circuit TC, whenback-bridge relay 1l energizes over the trunk line 1n series with'thepolarized supervisory relay 21 of the cord circuit CC, it reverses theconnections between the incoming talking conductors 7 land 9 and thewindings of line relay 10 for the purpose of transmittingback asupervisory signal which is of utility in certain cases, as is wellknown.

Back-bridge relay 11 also closes a multiple holding circuit for releaserelay 12 at its inner-upper armature; and at its middle-upper armatureit opens the locking circuit of the ring-start relay 15 'and closes anew cir.

vcuit for timer relay 16. T-he ring-start relay 15 n'ow falls back andterminates the application of ring-back-tone current to the lowertalking conductor 'to indicate to the subscriber that the operator hasresponded. The new circuit for relay 16 closed by contacts of relay 11includes. the o erated inner-upper armature of relay 17. hen relay 16operates at this time it closes a circuit through' the operatedinner-lower armature of relay 17 for thetone-cut-o relay4 13, whichrelay does not operatefor the time being because of the time intervalrequired for the vibrate ing Contact of the timer relay to stop itsvibration. and make continuous contact. As a further result of theoperation of back-bridge relay 13, the direct ground cony nectionnormally applied to the right-hand terminal of the lower winding .ofrelayll is replaced by a ground connection through the inner-lowerarmature of relay 11, normally closed contacts controlled bythevarmature of the tone-cut-off relay 13, and the lower winding of theinduction coil v14. By this connection, the 'characteristic tone currentflowing fromgthe secondary winding of the transformer 25 and through theoperating magnet 1 and associated relay 2 to the release trunk conductorof the established connection and thence to ground by Way of the upperwinding of the induction coil 14 causes a characteristictone current toflow to the talking circuit by yway of the lower winding of theinduction coil 14 and the` lower winding of the back-bridge relay 11.The 'tone produced by this flow of current may be heard by thesubscriber at substation A a'nd also by the operator, whereby theoperator learns what class the calling line is in.

Terminating the claas-tone current After the interval for which it isadjusted, the vibrating Contact of the timer relay 16 ceases to vibrate,whereupon the tone-cut-oif relay 13 responds and re-applies groundpotential directly tothe rightha'nd terminal of the lower winding ofback-bridge relay 11', at the same time open-circuiting the lowerwinding of the induction coil 14.

The momentary application ofthe distinci tive tone current has beenterminated, and the subscriber and operator ma now converse with eachother as desire following which the connection may be further ext-endedby Way of the cord circuitCC, in which case the relay 22 is caused tofall back and disconnect the operators headset conductors from thetalking strands of the cord circuit.

Repeating they tonevaignal In case vthe operator wishes to verify thetone signal initially heard, he may cause the tone signal to be repeatedby merely removing the plug P momentarily from the "ack J A and againinserting the plug. The e ect of Releasing the established connectionAfter the subscriber at substation A has replaced his receiver andcaused the operator to receive a disconnect signal at the lampcontrolled by the battery feed relay 21, when the connections to theback-bridge relay 11 are reversed, and the .operator has removed theplug P from the jack J and allowed the back-bridge relay 11 of the trunkcircuit TC to restore, the circuit of release relay 12 is finallyopened, whereupon relay 12 falls back and pei'mitsrelays 13, 16, and 17to restore, at the saine time disconnecting ground potential fromconductor-8 to permit the selector S to release and the lineswitch LS torestore to normal condition.

- lVhat is claimed is:

1. In a telephone system, a subscribers line identified by a distinctivetone, a trunk line, means for extending a call from said subscribersline to the trunk line, means for answering the call, and means forapplying said tone to the trunk line and for removing thel sameresponsive to the answering of the ca 2. In a telephone system, a\subscribers line, a source of tone associated with said line, a trunkline, means for extending a call from said subscribers line to saidtrunk line, means for answering the call, means operative for connectingsaid tone source to the trunk line and for subsequently disabling thetone source, and means responsive to the answering of the call foroperating said last means. v

3. In a telephone system, two exchanges, an interconnecting trunk line,means in one exchange for extending a call to the other exchange viasaid trunk line, means inthe other exchange for answering the call, asource of tone in said one exchange, and means responsive to theanswering of the call for momentarily applying tone from said source tothe trunk line and for then terminating the application. v

4. In a telephone system, two exchanges, an interconnecting trunk line,means in one exchange for extending a call to the other exchange viasaid trunk line, a link circuit in said other exchange for answering andfurther extending the call, a source of tone in said one exchange. andmeans responsive solel -to the connection of said link to the trun linetoanswer the call for connecting said tone source to the trunk line andfor disconnecting it at the end of a predetermined interval.

5. In a telephone system, a trunk line con-- nectin an automaticexchange and a manual switch card, subscribers lines of differentclasses in the automatic exchange, the lines of each class beingidentified by a separatev tone supplied by tone sources associated withthe lines, means for extending a connection from a calling line to theswitchboard via said trunk line, a link circuit at the switchboardadapted to connect with the trunk line for answering the call, and meanswherebyv v-tors and for then` disconnecting them at the end of a shortinterval.

7. In a telephone system, a trunk `line extending from a firstswitchboard to a second switchboard, said second switchboard being amanual switchboard, means at the first switchboard for extending aconnection to said trunk line and for signalling the operator at thesecond switchboard over said trunk line, means under the control of theoperator at the second switchboard whereby the operator can respond tothe said signal `by placing herself -in telephonie communication withthe trunk line, means also responsive to the last named means forsetting up a supervisory condition over said trunk line, means at thefirst switchboard for making a momentary characteristic application oftone current to said trunk line, and means respon-V sive to saidsupervisory condition being set up for initiating the operation of thelastnamed means.

8. In a telephone system, a line identified by a distinctive tone, atrunk line extending to a manual switchboard, means for extending a callfrom said line to said trunk line, means including a plug and a jack atsaid switchboard for answering said call, and means responsive to theinsertion of the plug into the jack pursuant to the answering of thecall for initiating and terminating a momen- JOHN A. BURGENER.

